Production of fertilizers



UNITED STATES PATENT OFFICE PRODUCTION F FERTILIZERS Heinrich Tramm an Holten, Germany, Aktiengesellschaft, many Application November 9 In Germany N 8 Claims.

Our invention relates to fertilizers and more particularly to means whereby fertilizers containing nitrogen and phosphorus alone or in combination with other fertilizing constituents can 5 be produced in a simpler and more eihcient manner than was hitherto possible.

As is well known to those skilled in the art, the production on a large scale of fertilizers containing, amongst other fertilizing constituents, also 10 phosphate of ammonia, is connected with certain diiiiculties which result from the fact that solid diammonium phosphate (NH4)2HPO4 could not be obtained directly. One of the principal diiiiculties encountered in the production of diam- `monium phosphate results from the fact that the production of highly concentrated phosphoric acid by acting with acids on mineral phosphates is not an easy matter since the mineral phosphates can only be decomposed for the recovery of free phosphoric acid by acting thereon With comparative- 1y dilute acids, this being due to the necessity of effecting the decomposition in the presence of so much liquid that the suspension resulting in the reaction can readily be iiltered. Apart therefrom the Washing out of the products of decomposition, even if it is carried out in countercurrent, requires great quantities of water so that normally only a phosphoric acid of about 30% is obtained. In trying to concentrate this dilute phosphoric acid by evaporation other difculties are encountered, which are created by the hydrofluoric acid admixed to the phosphoric acid and which is known to vigorously attack all vessels including ceramic vessels, when operating at high temperatures. A11 these reasons lead in many cases to the more expensive production of phosphoric acid by reduction of the phosphates and conversion of the phosphorus formed in this reaction in the gas phase into concentrated phosphoric acid.

We have now found that it is easily possible to produce solidphosphate of ammonia frommdilutem, phosph"V ,iccidlbylactiiig i,jdhiixturesjmmnitric acid andvphospl'ioric acidwwithsammgnia vhereby' ammonium phosphateand,ammoniummitrate are produced4 inpneoperation. E

The new process according to this inventio-n involves the further advantage that theaminonium phosphate thus obtained is mixed with ammonium nitrate..whichaisronehpf lthe most valuable cohstituents of rmixed fertilizers.

In the operation of our invention we prefer introducing simultaneously into the reaction vessel the ammonia and the mixture of phosphoric and nitric acids, utilizing the heat of reaction for concentrating the mixture. If a phosphoric acid d Carl Clar, Oberhausenassignors to Ruhrchemie Oberhausen-Holten, Ger- 1932, Serial No. 641,887

ovember 12, 1931 (Cl. 'Y1-9) of low concentration, such as can readily be produced, is used in this operation, the heat of reaction may not be sufficient to completely evaporate the water introduced together with the acids, and in such case We prefer providing means for supplying heat from without either to the neutralizing vessel itself or to a separate vessel. In all cases care is taken to add the reagents in such proportions that the mixture is substantially neutral. We further prefer to operate in such man- 10 ner that in spite of the evaporation of the water no solid ammoniumhitrate separates out, but remains in thepriduct of reaction in molten condition, serving as a means for suspending and transporting'the solid phosphate which separates 15 out.

Obviously the water contained in the phosphoric acid is here evaporated within the reaction mixture which has no corrosive action, and this water can be evaporated completely since, although the 20 Whole of the ammonium phosphate produced in the reaction is solid, the practically anhydrous molten ammonium nitrate acts as a means for suspending the ammonium phosphate, so that here the supply of heat from Without, which is neces- 25 sary in order to maintain the reaction mixture in a state of fluidity such that the danger of clogging of the pipes does not arise, does not encounter any difficulties.

During the reaction the mass should be vigor- 30 ously stirred in order to maintain an intimate mixture. Preferably the mixture of molten ammonium nitrate and solid ammonium phosphate is withdrawn by means of an overow or the like, in proportion as it is formed. 35

'I'he principal advantage oiered by this process lies in the production of a solid product being a mixture of ammonium phosphate and ammonium nitrate, which is formed directly on solidification of the reaction mixture.

If it is desired to produce mixed fertilizers we prefer addingthapotassiunr sa1ts,.cal ciumM nsalts, c1 ayey or ,humusdike-.constituentiq.lie sdli'f' mbit@, ,niammniumni ,ateianaammcmum r phosphate, the mixture of the additional con- 4 stituents being heated so that during or after the mixture the ammonium nitrate is, at least partly, molten and the mass as a whole converted into a dough, which can then be caused to solidify by treating it on cooling cylinders, in cooling ysiorm- A` 50 conveyers orY the like, the flproduc,il-nleirig,g simultaneouslyvgrwsublsequentlygpuulated.

If it is desired toobtain a predetermined acidity -n the product, the mixing of the constituents may be effected in the presence of ammonia gas. 5

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In the drawing affixed to this specication and forming part thereof an apparatus adapted for use in the operation of our invention is illustrated diagrammatically by way of example in vertical section.

Referring to the drawing, I is the reaction vessel and 20 is a heating jacket surrounding the lower half of the vessel. 3 and 4 are funnels extending into the vessel and serving for introducing the nitric and phosphoric acids separately. 2 and 5 are pipes extending vertically into and in proximity of the bottom of the vessel, their bottom ends being connected with an annular perforated distributing member 2i through which ammonia gas is introduced. 22 is a stirrer driven by a belt 6. 'I is an overflow tube leading from the upper half of the vessel to the cylinder 8 surrounding a screw conveyer 23, 24 being a downwardly directed tube arranged at the outer end of the cylinder 8. 9 is a drum which can be heated from without as indicated by the burners 25 and I0 is a charging hopper serving for introducing the additional constituents of the mixed fertilizer, such as potassium salts, calcium salts, clay and the like. 26 is a discharge hopper. The discharge tube 24 and discharge hopper 26 are arranged above a hopper 21. II is a vessel arranged below the hopper 21 and provided with a sloping bottom 28. 29 is a heating coil arranged in the Vessel II, the windings of the coil being spaced in such manner that gaps I to 20 mms in width are formed between the windings of a coil. I3 is a horizontal shaft extending axially across the coil 29 and 30 are stirrer arms mounted on this shaft, which can be set rotating by driving means indicated at 3l. 32 is the cylindrical casing of a worm conveyer I5 extending below the bottom 28 of the vessel II and connected therewith by a connecting tube 33. I4 is a pipe serving for introducing ammonia into the cylinder 32.

In the operation of this apparatus the nitric and phosphoric acids are introduced into the vessel I through the tunnels 3 and 4, respectively, while ammonia gas is introduced through the pipes 2 and 5, issuing from the perforations of the distributor 2l and rising in the acid liquid, which is heated by the steam or hot liquid circulating in the jacket 29, to make up for any deficiency in heat beyond the heat of neutralization. The moist hot mixture of ammonium nitrate and diammonium phosphate forming in the reaction escapes from the vessel through the overflow tube 1 and is cooled in passing through the windings of the worm conveyer 8, dropping thereafter into the hopper 21 intowhich the additional constituents of the fertilizer to be produced, such as potassium or calcium salts, clay or the like, are distributed from the drum 9. The combined ammonium salts and other constituents are deposited on the heating coil 29 and being heated thereon are converted into a thickly fluid mass, the ammonia salts in the mixture being partly molten. The'viscous mixture passing through the gaps between the windings of the heating coil 29 is caught and thoroughly worked through by the arms 30 of the stirring device operating within the coil, and escape from between the windings of the coil to drop onto the bottom 23 of the vessel and escape into the casing 32 of the conveyer worm I5, to be exposed therein, if desired, to the action of ammonia gas introduced through pipe I4. In the conveyer worm I5 the mixture is worked through and allowed to cool and is discharged at the outer end of the casing.

In practising oui` invention we may Ol nstance proceed as follows:

E xample 1 Neutralization of the nitric and phosphoric acids is effected in the closed heated Vessel I which may for instance have a capacity of 500 litres. First of all a molten mixture heated to 115 C. is filled into the vessel, consisting of 45% ammonium nitrate, 47% diammonium phosphate and 8% water. To this mixture is now added hourly a mixture of 47 kilograms-:35.7 litres of a 50% nitric acid and 45.8 kilograms=34.0 litres of a 50% phosphoric acid. At the same time so much ammonia gas is introduced through the pipes 2, 5, that 13.7 kilograms NH3 are absorbed per hour. During this operation the mixture in the vessel is kept ,constantly at 115 C. 64.8 kilograms of the molten mixture of ammonium nitrate and diammonium phosphate containing '7.3% water escape per hour through the overflow 'I in the form of a thin liquid and in this manner about 4 tons of a solid mixture can be recovered per day and cubicmetre capacity. The product is allowed to cool and solidify in the conveyer worm casing 8 and is thereafter mixed with 37 kilograms solid commercial potassium chloride containing 92% KCl. The mixture of the solid salts in passing through between the windings of the heating coil 29 is partly melted again and after having been worked through in the vessel I I by the agitating device is allowed to drop into the conveyer worm below the coil where it is allowed to cool down. If desired ammonia gas may be introduced through the pipe I4, while the mixture is dried and allowed to solidify.

There are thus obtained about kilograms of a mixed fertilizer containg about 16.5% N, 16.5% P205 and 21.5% KzO.

Example 2 The neutralizing vessel having been filled with a molten mass heated to about C., which is composed of 64% diammonium phosphate, 29% ammonium nitrate and '7% water, a mixture of 50.6 kilograms of a 30% phosphoric acid and 14.4 kilograms of a 50% nitric acid are introduced per hour, together with a quantity of ammonia gas sufficing to neutralize these acids. While the operation is proceeding, the temperature of the mixture in the vessel is maintained constant at about 115 C. About 6.6 kilograms ammonia are absorbed per hour and about 31.3 kilograms of a moist salt mixture containing ammonium nitrate and diammonium phosphate escape through the overflow, to be mixed, after cooling and solidiiication, with a mixture heated to about 100 IC,.- of 58 kilograms potassium nitrate of 98% and 10 kilograms whitewclay free from carbonate. In passing through the coil 29 the mixture is heated to about 90 C. and is thereafter allowed to cool down and solidify in the conveyer worm I5. There are thus obtained per hour about 100 kilograms of a mixed fertilizer containing about 15% N, 11% P205, and 26.5% KzO.

Example 3 To a molten mixture of 36% diammonium phosphate, 56% ammonium nitrate and 8% water are added hourly at 115 C. in the reaction vessel 71.6 kilograms of a 25% phosphoric acid, 53% oi a 55% nitric acid and the quantity of ammonia required for the absorption of 13.5 kilograms of the gas. Through the overflow there escape per hour about 64 kilograms of the mixture of moist ammonium nitrate and diammonium phosphate, which is now allowed to cool and solidify, whereupon 35.6 kilogramspotaxs-, and 10 kilograms ,dieal-v ailiiithlelide 0f 98 o ein 'wpliosppllate are added. IThe mixture in passing through thel 4` coil 25 is heated to 90-100 C., whereby the ammonium salts present in the mixture are partly melted. After cooling down in the conveyer worm below the heating coil about 108 kilograms of a mixed fertilizer are obtained per hour, which contains about 16.2% N, 12.0% P205, and 20.4% KzO.

Obviously the vessel l and the drum 9 may be heated in a different manner than here shown, and the means for mixing and cooling the intermediary and nal products may be varied Without departing from the spirit of our invention.

Apart from the apparatus here shown by way of example various changes may be made in the details disclosed in the foregoing specication without departing from the invention or sacricing the advantages thereof.

1. The method of producing a fertilizer comprising simultaneously introducing into a hot molten bods7 of ammonium nitrate and ammonium phosphate dilute nitric acid, phosphoric acid and ammonia gas in such proportion as to effect substantial neutralization of the acids, removing the mixture of ammonium nitrate and ammonium phosphate from the reaction zone, allowing said mixture to cool down and solidify and adding to the solid mixture of ammonium salts another fertilizing agent under conditions, under which at least one of the ammonium salts is partly melted.

2. The method of producing a fertilizer comprising simultaneously introducing into a hot molten body of ammonium nitrate and ammonium phosphate dilute nitric acid, phosphoric acid and ammonia gas in such proportion as to effect substantial neutralization of the acids, removing the mixture of ammonium nitrate and ammonium phosphate from the reaction zone, allowing the mixture to cool down and solidify, adding to the solid mixture of ammonium salts another fertilizing agent and heating to a temperature at which at least one of the ammonium salts is partly melted.

3. The method of producing a fertilizer comprising simultaneously introducing into a hot molten body of ammonium nitrate and ammonium phosphate dilute nitric acid, phosphoric acid and ammonia gas in such proportion as to effect substantial neutralization of the acids, removing the mixture of ammonium nitrate and ammonium phosphate from the reaction zone, allowing the mixture of ammonium salts to cool down and solidify, adding to it another fertilizing agent heated to a temperature, at which one of the ammonium salts is partly melted, applying heat to effect a partial melting of the mixture and allowing same to cool down and solidify.

4. The method of producing a fertilizer comprising simultaneously introducing into a hot molten body of ammonium nitrate and ammonium phosphate dilute nitric acid, phosphoric acid and ammonia gas in such proportion as to effect substantial neutralization of the acids, removing the mixture of ammonium nitrate and ammonium phosphate from the reaction zone, allowing the mixture of ammonium salts to cool dOWn and solidify, adding to it another fertilizing agent under conditions under which one of the ammonium salts is partly melted, and passing ammonia gas in contact with the mixture while the same is allowed to cool down and solidify.

5. The method of producing a fertilizer comprising simultaneously introducing into a hot molten body of ammonium nitrate and ammonium phosphate dilute nitric acid,phosphoric acid and ammonia gas in such proportion as to effect substantial neutralization of the acids, removing the mixture of ammonium nitrate and ammonium phosphate from the reaction zone, a1-

lowing the mixture to solidify, adding to the sol-4' id mixture of ammonium salts a lJQaSSiumsalt having fertilizing properties and heating to a temperature at which at least one of the ammonium salts is partly melted.

6. The method of producing a fertilizer comprising simultaneously introducing into a hot molten body of ammonium nitrate and ammonium phosphate dilute nitric acid, phosphoric acid and ammonia gas in such proportion as to effect substantial neutralization of the acids, supplying heat and removing the mixture of ammonium nitrate and ammonium phosphate from the reaction zone, allowing said mixture to cool down and solidify, adding to the solid mixture of ammonium salts another fertilizing agent and heating to a temperature at which at least one of the ammonium salts is partly melted.

'7. The method of producing a fertilizer comprising simultaneously introducing into a hot molten body of ammonium nitrate and ammonium phosphate dilute nitric acid, phosphoric acid and ammonia gas in such proportion as to effect substantial neutralzation of the acids, removing the mixture of ammonium nitrate and ammonium phosphate from the reaction zone, adding to this mixture of ammonium salts a calcium salt having fertilizing properties and heating to a ternperature at which at least one of the ammonium salts is partly melted.

8. The method of producing a fertilizer comprising simultaneously introducing into a hot molten body of ammonium nitrate and ammonium phosphate dilute nitric'acid, phosphoric acid and ammonia gas in such proportion as to effect substantial neutralization of the acids, removing the mixture of ammonium nitrate and ammonium phosphate from the reaction zone, adding to this mixture of ammonium salts a clayey substance having fertilizing properties and heating to a temperature at which at least one of the ammonium salts is partly melted.

HEINRICH TRAMM. CARL CLAR. 

